MASS AND CHARGE-DISTRIBUTIONS FOR THE REACTION CA-40-209 AT 600 MEV(BI)

The charge and mass of the projectile-like fragments produced in the 1 5-MeV per nucleon Ca-40+Bi-209 reaction were determined for products d etected near the grazing angle. Neutron number-charge (N-Z) distributi ons were generated as a function of the total kinetic energy loss and parametrized by their centroids, variances, and correlation coefficien ts. Although the initial system is very asymmetric, after the interact ion. a drift of the charge and mass centroids toward further asymmetry is observed. The production of projectile-like fragments is consisten t with a tendency of the projectile-like fragments to retain the Proje ctile neutron-toproton ratio (N)/(Z)similar or equal to 1 The correlat ion coefficient remains well below 1.0 for the entire range of total k inetic energy lost. Predictions of two nucleon exchange models, Randru p's and Tassan-Got's, are compared to the experimental results. The mo dels are not able to reproduce the evolution of the experimental distr ibutions, especially the fact that the variances reach maximum and the n decrease as function of the energy loss. This behavior supports the hypothesis that some form of projectile-like fragmentation or cluster emission is perturbing the product distribution from that expected fro m a damped mechanism.